Field of the Disclosure
Embodiments of the present invention relate to an organic light emitting device, and more particularly, to an organic light emitting device which facilitates to realize a long lifespan and to satisfy a color region.
Discussion of the Related Art
An organic light emitting device, which emits light in itself, is provided in such a structure in which a light emitting layer is formed between a cathode for injecting electrons and an anode for injecting holes. When the electrons generated in the cathode and the holes generated in the anode are injected into the light emitting layer, excitons are produced by the electron and hole bond. Then, when the exciton falls to a ground state from an excited state, the organic light emitting device emits light.
According to a direction of light emitted from the device, the organic light emitting device may be classified into a top emission type, a bottom emission type and a dual emission type. According to a driving method, the organic light emitting device may be classified into a passive matrix type and an active matrix type.
Unlike a liquid crystal display (LCD) device which requires an additional light source, an additional light source is not required for the organic light emitting device, whereby it is possible to manufacture the organic light emitting device to have a thin profile with lightness. Also, the organic light emitting device is driven by a low voltage so that the organic light emitting device is advantageous in an aspect of power consumption. In addition, the organic light emitting device enables great color reproduction, rapid response speed, wide viewing angle, and good contrast ratio (CR), and the organic light emitting device has attracted great attention as a next generation device.
With the advancement of high-resolution displays, the number of pixels for each unit area has increased, and a requirement for high luminance is increasing. However, there is a limitation of luminance (Cd) in each unit area (A) due to the emission structure of the organic light emitting device. Also, the increase of current applied to the organic light emitting device may cause problems such as the lowering of reliability and the increase of power consumption.
Accordingly, it is needed to overcome technical limitations in emitting efficiency, lifespan and power consumption that cause deterioration of quality and lowering of yield in the organic light emitting device. Furthermore, there are continuous studies for developing the organic light emitting device which enables to maintain great color realization, high emitting efficiency, long lifespan and wide viewing angle.
The organic light emitting device according to the related art has limitations of emitting efficiency and lifespan due to the emitting material for the organic emitting layer and the emission structure. Accordingly, various methods for improving the emitting efficiency and lifespan of the organic light emitting device have been proposed. However, when trying to improve the luminance, the power consumption is increased. Meanwhile, if changing the emitting material for improving the lifespan, the emission efficiency of the organic light emitting device is shortened.
If changing the emitting material of red, green and blue emitting layers so as to improve the emitting efficiency, the properties of color region and viewing angle do not meet a required standard.
The organic light emitting device of top emission type may obtain a desired color with high efficiency by amplifying light at a constant thickness of internal resonance by the use of a micro-cavity structure. However, even though it enables the high efficiency, it may have a high level of dependence on emitting dopant, and an intrinsic property of dopant may cause the change of luminescence-span (luminescence lifespan). Accordingly, a new structure for enabling the long lifespan of the organic emitting layer in the organic light emitting device has been studied.